Apparatus for applying discrete coatings

ABSTRACT

Apparatus and methods for producing intermittent, discrete patterns of coating material, such as hot melt adhesive, onto discrete substrates or substrate areas, where the patterns have sharp, square leading and trailing edges, as well as side edges. A slot nozzle die has elongated air slots along the slot extrusion opening. In the operation of the apparatus, the air flow is initiated from both air slots prior to the initiation of the hot melt flow. Also, the air flow is continued beyond that point in time, when the hot melt flow ceases. The delays between the operations of the air flow and the hot melt flow are on the order of micro seconds. Coating weights down to 1 gram per square meter at about 350 meters per minute substrate speed are provided. Alternatively, the lead and lag air start and stop times on each side of the coating material are different to control the exact disposition of the square cut-on and square cut-off coating edge on the substrate.

This application is a divisional of application Ser. No. 08/224,426,filed Apr. 8, 1994, U.S. Pat. No. 5,423,935, which is a continuation ofU.S. Ser. No. 07/910,781, filed Jul. 8, 1992, now abandoned.

This case is generally related to the following U.S. patent applicationsfiled on even date herewith:

    ______________________________________                                        Title              Inventors                                                  ______________________________________                                        Segmented Slot Die for Air                                                                       M. Gill; J. Benecke;                                       Spray of Fibers    A. Cieplik; T. Burmester                                   Ser. No. 07/910,784                                                           Apparatus & Methods for                                                                          J. Raterman; J. Benecke;                                   Applying Discrete Foam                                                                           A. Cieplik; T. Burmester;                                  Coatings           M. Gill                                                    Ser. No. 07/910,768                                                           Methods & Apparatus for                                                                          L. Hauser; J. Benecke;                                     Applying Coatings to Bottles                                                                     A. Cieplik; T. Burmester;                                  U.S. Pat. No. 5,354,378                                                                          M. Gill; K. Washington;                                                       R. Evans                                                   Apparatus & Methods for                                                                          B. Boger; J. Benecke;                                      Applying Conformal Coatings                                                                      A. Cieplik; T. Burmester;                                  to Electronic Circuit Boards                                                                     M. Gill                                                    Ser. No. 07/910,782                                                           Apparatus & Methods for                                                                          J. Raterman; J. Benecke;                                   Intermittently Applying                                                                          A. Cieplik; T. Burmester;                                  Discrete Adhesive Coatings                                                                       M. Gill                                                    Ser. No. 08/259,818                                                           ______________________________________                                    

Such applications are expressly incorporated herein by reference.

This invention relates to the application of coatings to substrates andmore particularly to the application to substrates of discrete, uniformcoatings having sharp, square cut-on and cut-off edges.

Many industrial applications require the use of discrete, well definedand uniform adhesive coatings applied to predetermined areas. Suchcoatings are very useful in varied lamination processes, such as bookbinding, for example, and in other coating operations such as conformalcoatings on non-uniform substrates like electronic circuit boards, andin other applications as well.

In the production of discrete coatings and adhesives for lamination ofdiscrete substrate areas, for example, it is desirable to obtain broad,uniform coatings in a non-contact application process with sharp,square, cut-on and cut-off edges with no stringing of material. None ofthe processes currently known are entirely suitable for thisapplication.

Many various devices have been used to apply adhesives for lamination,including contact coaters, curtain coaters, spray coaters, and, morerecently, fine line or spiral pattern application devices. Curtaincoaters do not generally provide acceptable cut-on and cut-offperformance. Also, they do produce unacceptable neck-in, causingthickening of applied coating at the edges, or "rail roading". Contactcoaters present the inherent disadvantage of wear and substrate indexand tension tolerances. The spray, fine line and spiral patternapplicators do not generally produce highly defined square edge cut-onand cut-off coating edges in a uniform broad coating, as are desired ina number of applications.

While not related to lamination applications generally, anothertechnique used for producing fibers and non-woven webs is known as amelt-blowing process. One such example of the melt-blowing process isdescribed in U.S. Pat. No. 4,720,252. In that device, hot meltthermoplastic material is extruded from a continuous slot opening andair is blown onto the extruding material from both sides of the slotopening to produce the desired webs. Such processes are used for webproduction, and do not generally concern themselves with intermittentoperation to produce discrete coatings, nor with extruding adhesives forlamination applications.

Accordingly, it has been one objective of this invention to producebroad, uniform, hot melt adhesive coatings with sharp side edges andsharp, square leading and trailing edges on intermittently presenteddiscrete substrate areas.

Another objective of this invention has been to provide methods andapparatus for intermittent non-contact application of thermoplasticcoating material, having sharp and square side, leading and trailingedges, to discrete, predetermined areas.

Another objective of the invention has been to provide slot nozzleapparatus and methods for producing broad, uniform discrete coatingshaving sharp and square side, leading and trailing edges.

To these ends, a preferred embodiment of the invention includes a slotnozzle, elongated air channels on each side of the slot nozzle forimpinging a flow of air on each side of an expanse of coating materialextruding or emanating from the slot nozzle, and means for controllingthe supply of material to the slot nozzle and the supply of air to theair channels so that each can be initiated and stopped at predeterminedintervals to produce sharp, square leading and trailing edges in thedeposited coatings.

In one mode, the air start-up on both sides precedes extrusion start-upand continues until after the extrusion is stopped. In another mode, theair on one side of the nozzle is started before extrusion is started andterminates before extrusion is stopped while air on another side of thenozzle starts at or after extrusion start-up and continues until afterextrusion stops.

Continuation of air flow after extrusion stoppage can draw coatingmaterial remaining at or in the nozzle into the air stream and onto asubstrate, causing stringing. Accordingly, the delay of air stoppageafter extrusion stoppage is predetermined to produce good sharp, squarecoating pattern cut-off, but not so long as to draw remaining glue atthe nozzle therefrom so as to cause stringing. The air start-up and stopdelays are preferably on the order of micro-seconds.

The invention produces uniform, wide or broad coatings with nosignificant edge thickening, having sharp side edges and sharp, square,leading and trailing edges coordinated with a predetermined underlyingsubstrate area and applied in a non-contacting application process.

These and other objectives and advantages will become readily apparentfrom the following detailed description of a preferred embodiment of theinvention and from the drawings in which:

FIG. 1 is a diagrammatic side view in partial cross-section illustratingthe invention;

FIG. 2 is an elevational side view in partial cross section of a slotnozzle coater according to the invention;

FIG. 3 is an elevational front view in partial cross-section of theapparatus of FIG. 2, illustrating diagrammatically control and flowfeatures of the invention;

FIG. 4 is an exploded view of the slot nozzle die of FIG. 2;

FIG. 5 is a diagrammatic view illustrating use of one embodiment of theinvention in a book binding application;

FIG. 6 is a front view of the slotted or segmented shim used in the slotnozzle die of the invention;

FIG. 6A is a front view of an alternate "open" shim used in the slotnozzle die of the invention;

FIG. 7 is a graph illustrating coating weight applied vs. substrate linespeed for a coater according to the invention;

FIG. 8 is a perspective exploded view of a disposable diaperillustrating use of the invention in the manufacture of consumable ordisposable products; and

FIG. 9 illustrates the sharp and square patterns of coatings attained bythe invention.

SPECIFICATION

Turning now to the drawings, there will now be described the apparatusfor generating discrete, uniform coatings having sharp and square cut-onand cut-off edges. According to the invention, such coatings are eitheropen, fibrous or porous coatings, or, on the other hand, are solidfilms. Moreover, such coatings can be formed from glue or adhesivematerials, such as hot melt adhesives, or from cold glues, paints, orother materials of adhesive or non-adhesive nature. The invention willbe described herein in terms of its use with hot melt adhesive.

FIG. 1 illustrates various features of a die means 30 and air and hotmelt adhesive controls according to the invention. The die means 30comprises two die halves 31, 32, and two air blocks 33, 34. Each diehalf 31, 32 includes a downwardly depending projection 35, 36. The diehalves 31, 32 define between them an extrusion slot 37. Slot 37 isdefined by the face 38 of the die half 31 and the face 39 of the diehalf 32. Face 38 is juxtaposed with respect to the face 39, as shown.The extrusion slot 37 terminates at an elongated slot or extrusionoutlet 40. As noted in the Figures, the air blocks extend below theoutlet 40 to provide a degree of protection from mechanical damage.

Die half 32 includes a hot melt passageway 41 for receiving hot meltadhesive and conducting the hot melt adhesive to a "coat hanger" portion42 of the die half 32, details of which are perhaps better seen in FIG.4. A slotted or segmented shim 45, as best seen in FIG. 6, and a portionof which is seen in FIG. 1, is located between the juxtaposed surfaces38 and 39 of the die halves 31 and 32. The shim 45 has a plurality ofelongated projections 46, extending at least proximate to the slotoutlet 40, defining between them a plurality of elongated channels orslots 47.

Each of the projections has a downstream tapered end portion 48, havinga tip 49 which is just short of, flush with or just outwardly of thelower edge 50 of the shim, and just short of, flush with or justoutwardly of the elongated slot nozzle extrusion outlet 40 (FIG. 1). InFIG. 1, only the top portion 51 of the shim 45 is shown, for the purposeof clarity. Alternatively, an open shim can be used. Such an open shimis depicted in FIG. 6A at 45a. This shim has an open area 45b, with noprojection 46. Also, in another alternative, the tapered end portion 48or tips 49 can extend beyond outlet 40, preferably two or threethousandths of an inch.

Returning now to FIG. 1, each of the upper die halves 31, 32 is providedwith an air passageway 55, 56, extending from an upper surface of thedie to a lower respective surface 57, 58. Each die half 31, 32 alsoincludes an inclined surface 59, 60, depending from the surfaces 57 and58, respectively. The inclined surfaces 59 and 60 define one part of anair passage, or elongated air slot 61 and 62, as will be described.

Turning now to the air blocks 33 and 34, it will be appreciated thateach of them include an inclined surface 63 and 64, respectively, whichdefine the other side of the air slots 61 and 62 with the juxtaposedrespective surfaces 59, 60, all as shown in FIG. 1. Each of the airblocks 33 and 34 include an upper surface 65, 66 juxtaposed to therespective lower surfaces 57 and 58 of the die halves 31, 32.

An elongated air plenum 67, 68 is formed in each of the air blocks 33,34. The plenums 67, 68 are also seen in FIG. 4. Respective air passages69 and 70 are formed in the respective air blocks 33 and 34 and extendfrom the respective surfaces 65 and 66 to a lower portion 71, 72 of therespective plenums 67, 68. Each of the plenums 67, 68 are primarilydefined in the air blocks 33 and 34. However, when the die means 30 areassembled, the top area of each of the respective plenums 67, 68 aredefined respectively by the lower surfaces 57 and 58 of the die halves31, 32. These surfaces 57, 58 also form an upper portion of air passage73 and 74, each of which respectively lead from their associated plenums67 and 68 to the air slots 61 and 62. Accordingly, looking at the righthand side of FIG. 1, it will be appreciated that air can pass throughthe passageway 55 to the passageway 69 in air block 33, and from thereto the plenum 67. "O"-rings, not shown, can be used at the interfaces ofthe respective die half and air block to seal passageways 55, 56 withpassageways 69, 70, respectively. Pressurized air in the plenum 67 movesthrough the passage 73 into the air slot 61.

In a like manner, air can be introduced to passageway 56 in the die half32 and from there it can move into the air passage 70 and into the lowerportion of the plenum 68. From the plenum 68, pressurized air isdirected through the air passage 74 into the air slot 62 of the airblock 34.

Referring now briefly to the upper portion of FIG. 1, it will beappreciated that a controller 75 is operationally connected to valvesV-1 and V-2, as shown, for controlling the introduction of heated,pressurized air to the passageways 55 and 56, respectively, in order topressurize those passageways and the downstream air passageways aspreviously described, with air. At the same time, the controller 75 isoperationally interconnected to a hot melt control valve 76 forcontrolling the supply of coating material, such as hot melt adhesive,to the hot melt adhesive passageways 41 and to the internal coat hangerarea 42 of the die means 30. While any suitable form of controller 75can be used, as is well known, one particular controller comprises aPC-10 pattern controller, manufactured by Nordson Corporation ofWestlake, Ohio. The PC-10 pattern control 75 is operational to initiateand to stop the generation of air into passageways 55 and 56, eithersimultaneously or independently, and also to initiate and to stop thehot melt flowing through valve 76 so as to intermittently providecoating material to the passageway 41 independently and at pre-selectedtimes with respect to the provision of pressurized heated air to thepassageways 55 and 56, all in a manner as will be described.

The air slots 61 and 62 are oriented on an angle with respect to theelongation of the extrusion slot 37. Accordingly, when coating materialis extruded through the slot 37 and outwardly of the extrusion outlet40, air moving through the air slots 61 and 62 is impinged on thematerial before that material engages or is deposited on an underlyingsubstrate which is presented for coating.

Turning now to FIGS. 2 and 3, there is shown more of the overallextrusion apparatus according to the invention. As shown in FIG. 2, thedie means 30 is interconnected with air valves V-1, V-2 and hot meltvalve 76, each of which is interconnected with an extrusion body 80which operationally interconnects the air and hot melt valves with thedie means 30.

For clarity, a portion of the air valve V-2 is shown in partial crosssection in FIG. 2. Since the valves V-1 and V-2 are identical, onlyvalve V-2 will be described. Such air valves are manufactured anddistributed by Nordson Corporation through Nordson Engineering,Luneburg, Germany, under part no. 265701. Any other suitable air valvecan be used.

Valve V-2 comprises a valve body 82 defining a valve chamber 83 and acontrol chamber 84, the two chambers being separated by the diaphragm85. An extension 86 having a bore 87 extending therethrough depends fromthe valve body 82 and extends into the bore 88 of extrusion body 80 toform an annular chamber 89 therewith. Chamber 89 is interconnected withan annular passageway 90 in the valve body 82, which interconnects withthe chamber 83. An annular chamber 91 is also defined in the valve body82 and interconnects with the chamber 83. When control air is directedinto chamber 84, the diaphragm 85 is pushed downwardly to seal off theannular passageway 90 from the annular chamber 91. On the other hand,when pressure is decreased in the control chamber 84, the diaphragmmoves upwardly to the position shown in FIG. 3. Air in the inlet annularchamber 89, which is heated and under pressure, communicates through theannular passageways 90 through the chamber 83 and the annular chamber91, into the outlet bore 87. Outlet bore 87 is connected through apassageway 92 to the air passageway 56 in the upper die half 32, asshown in detail in FIG. 1, where the air from there can move to theplenum 68 and into the air slot 62.

In like manner, the air valve V-1 is operable to selectively supply airto the air passageway 93 in the extrusion body 80 and from there to theair passageway 55 in the upper die half 31. Air moves through thatpassageway 55 into the plenum 67 and from there to the air slot 61.

The hot melt valve 76 can be any suitable hot melt valve which can beselectively controlled to initiate and to cut off the flow of coatingmaterial, such as hot melt adhesive, to the die means 30. One suchsuitable valve is balanced valve model no. EP51 produced by NordsonCorporation of Westlake, Ohio. Such valve minimizes significant changein pressures when the valve is switched between its opened and closedpositions. The valve 76 has a stem 96 seated over a port 97. Whencontrol air is supplied to an inlet 98, the stem 96 is lifted to permithot melt adhesive in a chamber 99 to flow through the port 97 and intothe hot melt passageway 41 of the upper die half 32. Hot melt adhesiveis introduced into the chamber 99 through hot melt inlet 100. A hot meltoutlet 101 is also interconnected with the chamber 99 to receivepressurized hot melt adhesive when the stem 96 is seated on port 97.

Any suitable apparatus can be utilized for melting and pumping hot meltadhesive to the valve 76. Such apparatus is shown diagrammatically at102. While any suitable apparatus could be utilized, one particular formof apparatus which is suitable is the model HM640 applicator,manufactured by Nordson Corporation of Westlake, Ohio.

It will be appreciated that the coating material may be preciselydelivered to the heads or nozzles by one or more material metering meanssuch as metering gear pumps. A single pump could feed a manifold for allthe heads or nozzles or a separate metering gear pump could be used foreach head or nozzle, or for a group of nozzles of less than all nozzles.This precise delivery permits accuracy in the material delivery so thataccurate basis weight coatings can be provided for varying substratespeeds, for example. Any suitable form of metering feeds can beutilized. For example, U.S. Pat. Nos. 4,983,109 and 4,891,249, expresslyincorporated herein by reference, disclose metering means for hot meltadhesives.

FIG. 3 illustrates diagrammatically the various control inputs to thevalves 76 and V-1. As shown in FIG. 3, the controller 75 isinterconnected to a control air supply 105 for supplying control air tothe valves V-1 and V-2. A pressurized air source 106 is interconnectedto an air heater 107 which supplies process air to the valves V-1 andV-2 for transmission to the respective air slots 61, 62, as describedabove. When the respective valves V-1 and V-2 are opened, controller 75is also interconnected to the control air supply for supplying controlair through closed and opened solenoid control valves (shown in FIG. 3)to open and close the hot melt valve 76.

Referring now more particularly to FIG. 1 and the details of the diemeans 30 as shown in FIG. 4, it will be appreciated that the plenums 67and 68 in the air blocks 33, 34 communicate with the lower surfaces 73Aand 74A, respectively, of the air passageways 73 and 74 as previouslydescribed, and air emanating from the upper portion of the plenums 67and 68 moves through the passageways 73 and 74 and then downwardlythrough the respective air slots 61, 62.

Turning now to the so-called "coat hanger" portion 42 of the upper diehalf 32, and with reference to FIG. 4, it will be appreciated that "coathanger" dies are known in general. For example, one coat hanger-type diefor handling hot melt adhesive is disclosed in U.S. Pat. No. 4,687,137,expressly incorporated herein by reference. The difference in thatstructure is that it serves a plurality of die outlets, and not acontinuous extrusion slot die as noted herein. While such a die could beused herein, nevertheless, the present die means 30 incorporates a "coathanger" portion 42 having an arcuate slot or groove of increasinglyshallow dimension 110 communicating with an incline surface 111. Surface111 is inclined such that its lower portion, where it meets bottomsurface 112, is closer to the plane of the face 39 than is the upperportion. It will also be appreciated that slot 110 is of decreasingdepth as its distance from port 113 continues until it flows unbroken insurface 111. The arcuate slot 110 of decreasing depth is fed by the hotmelt port 113, which is interconnected to the hot melt passageway 41. Inuse, when hot melt is supplied at pressure to the passageway 41, itexudes through the port 113 into the arcuate slot 110 and from thereflows over the surface 111 and spreads out throughout the relieved coathanger shaped portion 42 of the die face 39 and the side of the shim 45which is juxtaposed to the face 39 of the die half 32.

It will be appreciated that the slots 47 of shim 45 have upper endswhich communicate with the lower portion of the coat hanger die area 42,just above the surface 112 thereof, so that hot melt adhesive or othercoating material can flow into the slots 47 and then downwardly to theextrusion outlet 40. In this manner, the coating material is spreadthroughout the coat hanger portion 42 and across each of the upper endsof the slots 47 of the shim 45 at significantly equal pressures, so thatcoating material can move through the extrusion slot 37 within the slots47 of the shim 45 at relatively equal pressures.

As illustrated diagrammatically in FIG. 6, the material exudes throughthe slots 47 and then outwardly of the extrusion outlet 40.

Considering the advantages of the segmented shim 45, it will beappreciated that the width of the slot 47 between projections 46 ispreferably about twice the thickness of the shim. The thickness of oneshim 45 may be about 0.004" while the slot width, i.e. from oneprojection 46 across to the next projection 46, is about 0.008". Inanother shim 45, for example, the shim thickness is about 0.008" whilethe segmented slot width between juxtaposed projections is about 0.016"

Accordingly, the overall slot thickness between die faces 38, 39 can bedoubled while the die still produces the same basis weight coating as aprior slot die where the die slot is not segmented, as in thisinvention. Thus in a prior slot die where a slot thickness of 0.002" wasneeded for a small basis weight coating, the present invention canobtain the same basis weight coating with a slot thickness of 0.004", ordoubled. Thus, the slot die according to the invention could pass apotentially clogging particle of 0.003" while the prior continuous slotdie would not (for the same basis weight coating to be produced).

While the ratio of the shim thickness to the shim slot width ispreferably about 2 to 1, this ratio can be varied to produce varyingcoating thicknesses.

It will be appreciated that the width and thickness parameters of theshims 45, 45a and their components can widely vary. The parameters mayvary due to the basis weight of coating per square meter desired, thecohesiveness desired, the coating material viscosity or other factors.

In order to provide further description of one form of coat hangerportion 42, the surface 112 from face 39 back to surface 111 is about0.020" wide. The tops of slots 47 are about 0.050" when the shim isoperably disposed between faces 38, 39. The groove 110 at its deepestdepth from face 39 is about 0.125" from face 39. The surface 111 at itstop area is about 1/16" deep from face 111 and about 0.020" back fromsurface 39 at its bottom. The coat hanger width across face 39 is about38 mm.

It will also be appreciated that the overall die head could be expandedin length with, for example, open areas in the shim so that a wide,unbroken coating of greater than 38 mm could be obtained. In thisregard, several nozzles, each about 38 mm wide, could be closely spacedin adjacent fashion with very narrow lands therebetween to produce awide pervious or impervious film as disclosed herein.

Turning now to the use of the apparatus described above, for theapplication of coatings to defined predetermined or discrete substrates,it will be appreciated that the apparatus is capable of impinging hotair from the slots 61 and 62 on each side of the coating materialexuding from the extrusion outlet 40. The impinging air engages andshreds the energizing expanse of coating material into discretemicro-denier fibers. Edge control is uniform and the density of thepattern can range from 25% open or fibrous to 0% open, i.e. a non-porousfilm. The parameters are selected depending on the application to whichthe coatings are to be applied. The controller 75 is operational tostart and stop the application of air to the extruded coating materialat different times and/or intervals compared to the starting andstopping of the delivery of hot melt adhesive to the extrusion outlet40.

For example, in one preferred method of operation, the flow of airthrough the slots 61, 62 is started a short time prior to the time whenthe valve 76 is operated to initiate the delivery of coating materialinto the slot 37 and out through the outlet 40. The air is continued forthe coating deposition, shredding or fiberizing the extruding materialand carrying it to or spraying it on a substrate. At the end of thedeposition period, the valve 76 is first operated to cease the extrusionof coating material through the outlet 40. After a short delay, the flowof air through the slot 61 and 62 is stopped. While the amount of delayin such an operation will vary, depending upon the properties of the hotmelt, such time period generally will preferably be on the order ofmicro seconds. One example would be, for example, 1700 micro secondsbetween the start up of the air and the start up of the extrusion of thehot melt material, and 2100 micro seconds between the stopping of thehot melt material and the stopping of the air. Continuation of the airflow much beyond this time might serve to pull off remaining hot meltadhesive at the extrusion outlet and cause stringing of the depositedcoating.

Moreover, it will also be appreciated that the invention contemplatesthe selective applications of air flow through either slot 61 or 62individually or together during the deposition period, particularly tomore accurately define the initial and ending contact position of thedeposited coating on the substrate. One such mode of operation isillustrated in FIG. 5, where the apparatus is utilized, for example, toapply a discrete coating to the spine of a book so that a cover can beapplied or laminated thereto.

In FIG. 5, a book having a spine with no adhesive thereon is shown atthe left hand side of the figure at position B-1. As illustrated at B-1,air flow has been initiated through slot 61 but there is no coatingmaterial being extruded through the slot 37 and no air flow has startedthrough the air slot 62. Moving to the book at the position B-2, it willbe appreciated that the hot melt flow has started and that it isimpinged by air flowing through slot 61. Since the air flowing throughslot 61 moves downwardly in a general right to left direction as shownin FIG. 5, it will be appreciated that the coating material does notstring down the side of the book pages but is applied directly to theedge of the spine of the book with no stringing. Thereafter, and formost of the remainder of the coating operation, as shown in bookposition B-3, air flow is initiated through the slot 62. At the end ofthe coating operation, the air flowing through slot 61 is terminatedjust before termination of the extrusion of the coating material(position B-4). Then, as shown in position B-5, the coating materialflow has ceased, while the air flowing through slot 62 continues for ashort time period thereafter. This operation, when used in book binding,for example, would ensure that the adhesive will not string down theleading or rear sides or ends of the book.

Accordingly, with respect to FIG. 5, the lag air is started first andstopped first and the lead air, that is, with respect to the machinedirection of the application as shown in FIG. 5, is started after theextrusion of the coating material and stopped after the coating materialextrusion has ceased. In this way, the air angling onto the coatingmaterial does not blow it in strings over the edges of the book, aswould be undesirable and yet the cut-off and cut-on edges of the coatingmaterial are maintained in sharp, square fashion on the spine of thebook.

It will also be appreciated that the invention is useful in manyapplications. In one particular application, the invention is useful inapplying adhesive to components of a consumable product, such as adisposable diaper made up from impervious synthetic films, non-wovenabsorbent material or "fluff" and elastic for waist and leg areagatherings.

In FIG. 8, a disposable diaper 150 is illustrated in exploded view,showing its typical components. The diaper includes an impervious outersheet 151, an absorbent non-woven or "fluff" layer 152, a "fluff" tissuecover 153, a pervious cover sheet 154, elastic waist bands 155,elongated elastic strands 156, 157, and fastening tapes 158.

Lines of adhesive are applied by the apparatus described herein, ineither fibrous or impervious form, to hold the diaper componentstogether. For example, lamination of the outer sheet 151 to the tissuecovered "fluff" 152 is accomplished by application of adhesive stripesor bands at 160, 161 and 162. Adhesive bands 163 are applied tostabilize the "fluff" 152 to tissue 153. Adhesive bands 164 are appliedfor securing elastic waist bands to the diaper 150. Adhesive bands 165are applied over elastic strands in the leg and interior areas. Adhesivebands 166 are applied to adhere the non-woven tissue covered "fluff" 152to the cover sheet 154. Adhesive bands 167 are applied to hold theelastic strands 156 to cover sheet 154 and for end tack at the leggather area of the diaper.

As shown in FIG. 8, the adhesive bands or stripes 160-167 are varied inwidth. They can be applied by apparatus as disclosed herein orientedalong a diaper manufacturing line at predetermined positions asnecessary, with sharp and square side and leading and trailing edges.

The invention is believed useful in many other applications and with awide range of coating materials of different viscosities, as shown bythe following two examples.

ADHESIVE NO. 1

This adhesive had the following viscosities at the followingtemperatures:

41,700 centipoise at 275 degrees F.

25,050 centipoise at 350 degrees F.

16,575 centipoise at 325 degrees F.

11,325 centipoise at 350 degrees F.

Operating temperature was at 180 degrees C. With a 0.1 millimeter thickshim in the head, the supply pressure was 20 BAR, the return pressure ofthe adhesive was 21 BAR, and the air pressure was 1.5 BAR. The air wasturned on 2 millimeters of substrate travel before the adhesive andturned off 2 millimeters of substrate travel after the adhesive.Substrate line speed is about 150 meters/minute. This corresponds to thedelay times of about 800 micro seconds. At these settings, the cut-onand cut-off were square and sharp and a coating weight was produced of 5grams per square meter of uniform thickness.

ADHESIVE NO. 2

This adhesive had the following viscosities:

5,700 centipoise at 250 degrees F.

2,600 centipoise at 275 degrees F.

1,400 centipoise at 300 degrees F.

800 centipoise at 325 degrees F.

550 centipoise at 350 degrees F.

Operating temperature was 300 degrees F. Coating weight was 15 grams persquare meter. Cut-on and cut-off were square and sharp with nostringing.

It is important in both these examples and other applications that thehot melt supply pressure and return pressure be maintained in arelationship, such that the differences of the two pressures are notmore than 1 BAR.

In addition, it is believed, based on current information, that aminimum flow rate is required to produce a uniform pattern with squareand sharp cut-ons and cut-offs. For example, in connection with a 38millimeter wide pattern, it is possible to get down to at least 1 gramper square meter of coating weight at approximately 350 meters perminute of line speed. The graph in FIG. 7 illustrates coating weightswhich have been obtained with a 38 millimeter wide pattern deposited ona substrate moving at about from 70 meters per minute to about 350meters per minute, with the shaded area of the graph (FIG. 7)illustrating the proven operating ranges.

As noted above, coatings are produced in varying weights. Such coatingscan be varied from 0% open or impervious to about 25% open or porous.

It will be appreciated that various sizes, spacings, pressures andselections of materials can be utilized. Thus, for example, the hot meltmight be started at 2 mm of substrate movement after air start up, andthe air flow stopped at 5 mm of substrate movement beyond extrusion shutoff, for substrate speeds of about 70 meters/minute.

It will also be appreciated that the particular coating pattern producedby the apparatus and methods described above can either be porous orimpervious and that the coating patterns are preferably produced in adiscrete fashion on discrete substrates, for example, with good, square,sharp cut-on and cut-off and no stringing for the leading or trailingedges of the pattern, while at the same time, the sides of the patterndeposited are also parallel and sharp.

FIG. 9 illustrates the sharp edged, square coating patterns attainablewith the invention. In FIG. 9, discrete adhesive coatings 170-173 havebeen applied by the invention to a substrate 174. Each discrete coatinghas two sharply defined side edges 175, 176, a sharply defined leadingedge 177, and a sharply defined trailing edge 178. Sides 175, 176 aresquare to leading and trailing edges 177, 178. There is substantially nostringing.

Accordingly, the invention provides for intermittent non-contact coatingoperation with sharp, square-edged patterns and no stringing for avariety of applications, including lamination of the substrate to whichthe patterns are applied to some other substrate or component. These andother modifications and advantages of the invention will become readilyapparent to those of ordinary skill in the art without departing fromthe scope hereof, and the applicant intends to be bound only by theclaims appended hereto.

We claim:
 1. Apparatus for producing a coating for noncontactapplication to a substrate, said apparatus comprising:a slot nozzlehaving an elongated slot outlet through which a coating material can beextruded for deposition on a substrate spaced from said slot nozzle; atleast one elongated air slot proximate said slot outlet for impinging atleast one air flow onto a coating material exuding from said slotoutlet; and means for starting the flow of air prior to extrusion ofcoating material from said slot outlet said flow of air producing adiscrete coating which when deposited on a substrate has square, sharpleading and trailing edges.
 2. Apparatus as in claim 1 further includingmeans for stopping the flow of air after extrusion of coating materialhas ceased.
 3. Apparatus as in claim 2 including at least two air slots,one proximate each side of said slot outlet for impinging air therefromonto coating material exuding from said slot outlet.
 4. Apparatus as inclaim 3 further including means for delaying impinging air from one ofsaid air slots until after coating material exudes from said slot outletand for continuing flow of air from said one slot until after extrusionof said coating material has ceased.
 5. Apparatus as in claim 4 furtherincluding means for initiating flow of air from the other air slotbefore coating material is extruded and for ceasing flow of air fromsaid other air slot before extrusion of said coating material ceases. 6.Apparatus as in claim 1 wherein said slot nozzle is disposed in a slotnozzle die comprising:die halves defining an extrusion slottherebetween, said die halves having tapered projections with parallelinward facing surfaces forming said extrusion slot and tapered outerwalls respectively partially defining inward surfaces of two airchannels disposed at an angle with respect to said extrusion slot; twoair blocks, each having a tapered surface juxtaposed in operativedisposition near one of said tapered outer walls such that one of saidair channels is formed therebetween; an air plenum in each said dieblock; an air passage in each air bock interconnecting and upper portionof each said plenum with a respective air channel; and an air passage ineach air block for feeding air to a lower portion of each said plenum.7. Apparatus as in claim 6, including an air passage in each die half,each die half air passage operationally interconnected with one of saidair passages in said air blocks for feeding air to said plenum therein.8. Apparatus as in claim 6 wherein said air passages for feeding airchannel are defined by juxtaposed surfaces of said respective die halvesand air blocks.
 9. Apparatus as in claim 6 wherein said respective airplenums are defined by juxtaposed surfaces of said respective die halvesand air blocks.
 10. Apparatus as in claim 6 wherein said extrusion slothas an outlet and further including a shim disposed between said diehalves.
 11. Apparatus for adhering together components of disposablediapers each having an impervious outer sheet, an absorbent layer andelastic members for waist and leg holes, said apparatus having:a slotnozzle having an elongated slot outlet through which a coating materialcan be extruded; at least one elongated air slot proximate said slotoutlet for impinging at least one air stream onto an adhesive coatingmaterial exuding from said slot outlet prior to deposition on one ofsaid components; and means for starting the flow of air prior toextrusion of adhesive coating material from said slot outlet whereinsaid coating when deposited on one of said components has at least onesquare sharp edge.
 12. In apparatus for laminating two componentstogether, the combination of:a slot nozzle having an elongated slotoutlet through which an adhesive coating material can be extruded ontoone component for receiving another component in adhesive relationthereto, said slot nozzle being spaced from said one component; at leastone elongated air slot proximate said slot outlet for impinging at leastone air flow onto an adhesive coating material exuding from said slotoutlet prior to contacting said one component; and means for startingthe flow of air prior to extrusion of adhesive coating material fromsaid slot outlet wherein said adhesive coating material, when deposited,has at least one square, sharp edge.
 13. An apparatus for producing acoating for application to a substrate, the apparatus comprising:a slotnozzle having an elongated slot outlet through which a coating materialcan be extruded; at least one air slot proximate the slot outlet, theone air slot impinging at least one process air stream onto the coatingmaterial exuding from the slot outlet to shred the material into fibersfor deposition onto the substrate; a diaphragm havingone side in contactwith control air for operating the air valve, and an opposite side inselective contact with at least one of the inlet and the outlet ports,the diaphragm being responsive to the control air to selectivelyoperatively open the ports into fluid communication with the each other,thereby initiating a flow of process air through the ports to the oneair slot and operatively close the ports from fluid communication witheach other, thereby terminating the flow of process air to the one airslot.
 14. The apparatus of claim 13 further comprising:a second air slotproximate the slot outlet, the second air slot impinging a secondprocess air stream onto the coating material exuding from the slotoutlet; a second diaphragm operated process air valve, the air valvehavinga second inlet port in fluid communication with a source ofprocess air, a second outlet port in fluid communication with the secondair slot, and a diaphragm havingone side in contact with control air foroperating the air valve, and an opposite side in selective contact withat least one of the second inlet and second outlet ports, the diaphragmbeing responsive to the control air to selectively operatively open thesecond inlet and second outlet ports into fluid communication with theeach other, thereby initiating a flow of process air through the secondinlet and second outlet ports to the second air slot and, operativelyclose the second inlet and second outlet ports from fluid communicationwith each other, thereby terminating the flow of process air to thesecond air slot.
 15. An apparatus for producing a coating forapplication to a substrate, the apparatus comprising:a slot nozzlehaving an elongated slot outlet through which a coating material can beextruded; at least one air slot proximate the slot outlet for impingingat least one air stream onto a coating material exuding from the slotoutlet; an air valve havingan inlet chamber connected to a source ofprocess air; an outlet chamber connected to air slots of a die; a valvechamber connecting the inlet and outlet chambers; a control chamberconnected to a source of control air; a diaphragm located between theinlet chamber and the outlet chamber and separating the control air fromthe process air, the diaphragm havinga first position providing fluidcommunication between the inlet and outlet chambers through the valvechamber, thereby opening the air valve and supplying process air to theair slots of the die, and a second position in response to control airof a predetermined pressure being introduced into the control chamber,the second position blocking fluid communication between the inlet andoutlet chambers through the valve chamber, thereby closing the air valveand stopping the supply of process air to the air slots of the die. 16.An apparatus for applying a coating having sharp, square cut-on andcut-off edges to a substrate, the apparatus including a noncontact diehaving a slot nozzle with an elongated slot outlet through which acoating material can be extruded and a first air slot proximate the slotoutlet for impinging at least one air stream onto a coating materialexuding from the slot outlet, the apparatus further comprising an airvalve includingan inlet connected to a source of process air; an outletconnected to the first air slot; a valve chamber selectively providingfluid communication between the inlet and the outlet; a control chamberconnected to a source of control air; a diaphragm located between thecontrol chamber and the valve chamber and separating the control airfrom the process air, the diaphragm being selectively movable betweenafirst position in response to control air of a first predeterminedpressure in the control chamber, the first position providing fluidcommunication between the inlet and outlet through the valve chamber,thereby supplying process air to the first air slot, and a secondposition in response to control air of a second predetermined pressurein the control chamber, the second position blocking fluid communicationbetween the inlet and outlet, thereby stopping the supply of process airto the first air slot.
 17. An apparatus for applying a coating to asubstrate, the apparatus including a noncontact die having a slot nozzlewith an elongated slot outlet through which a coating material isextruded and at least one air slot proximate the slot outlet forimpinging at least one air stream onto a coating material exuding fromthe slot outlet to engage and shred the coating material into discretefibers, the apparatus further comprising an air valve includingan inletconnected to a source of process air; an outlet connected to the firstair slot; a valve chamber selectively providing fluid communicationbetween the inlet and the outlet; a control chamber connected to asource of control air; a diaphragm located between the control chamberand the valve chamber and separating the control air from the processair, the diaphragm being selectively movable betweena first position inresponse to control air of a first predetermined pressure in the controlchamber, the first position providing fluid communication between theinlet and outlet through the valve chamber, thereby supplying processair to the first air slot, and a second position in response to controlair of a second predetermined pressure in the control chamber, thesecond position blocking fluid communication between the inlet andoutlet, thereby stopping the supply of process air to the first airslot.
 18. The apparatus of claim 17 further having a second air slot,one of the fist and second air slots being proximate each side of theslot outlet for impinging air from the air slots onto both sides of thecoating material exuding from the slot outlet, the apparatus furthercomprising a second air valve includinga second inlet connected to asource of process air; a second outlet connected to the second air slot;a second valve chamber selectively providing fluid communication betweenthe inlet and the outlet of the second valve; a second control chamberconnected to the source of control air; a second diaphragm locatedbetween the second control chamber and the second valve chamber andseparating the control air from the process air within the second valve,the second diaphragm being selectively movable betweena first positionin response to control air of a first predetermined pressure in thesecond control chamber, the first position providing fluid communicationbetween the second inlet and the second outlet through the second valvechamber, thereby supplying process air to the second air slot, and asecond position in response to control air of a second predeterminedpressure in the second control chamber, the second position blockingfluid communication between the second inlet and the second outlet,thereby stopping the supply of process air to the second air slot. 19.An apparatus for producing a coating for application onto a diapercomponent, the apparatus comprising:a slot nozzle having an elongatedslot outlet through which a coating material can be extruded; at leastone air slot proximate the slot outlet, the one air slot impinging atleast one process air stream onto the coating material exuding from theslot outlet to shred the material into fibers for deposition onto thediaper component; a diaphragm operated process air valve, the air valvehavingan inlet port in fluid communication with a source of process air,an outlet port in fluid communication with the one air slot, and adiaphragm havingone side in contact with control air for operating theair valve, and an opposite side in selective contact with at least oneof the inlet and the outlet ports, the diaphragm being responsive to thecontrol air to selectively operatively open the ports into fluidcommunication with the each other, thereby initiating a flow of processair through the ports to the one air slot and, operatively close theports from fluid communication with each other, thereby terminating theflow of process air to the one air slot.
 20. A method of applying acoating material to a component of a disposable diaper comprising thesteps of:extruding a coating material from an elongated slot nozzle;selectively opening and closing a diaphragm operated valve to controlthe flow of process air from a source of process air to an air slotproximate the slot nozzle; impinging air through the air slot ontoextruding coating material to produce discrete fibers of coatingmaterial; and then depositing the discrete fibers of coating materialonto the component of the diaper.